﻿// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System.Drawing;
using System.Windows.Forms.VisualStyles;

namespace System.Windows.Forms;

/// <summary>
///  This is a rendering class for the TrackBar control.
/// </summary>
public static class TrackBarRenderer
{
    // Make this per-thread, so that different threads can safely use these methods.
    [ThreadStatic]
    private static VisualStyleRenderer? t_visualStyleRenderer;
    private const int LineWidth = 2;

    /// <summary>
    ///  Returns true if this class is supported for the current OS and user/application settings,
    ///  otherwise returns false.
    /// </summary>
    public static bool IsSupported => VisualStyleRenderer.IsSupported; // no downlevel support

    /// <summary>
    ///  Renders a horizontal track.
    /// </summary>
    public static void DrawHorizontalTrack(Graphics g, Rectangle bounds)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.Track.Normal, 1);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical track.
    /// </summary>
    public static void DrawVerticalTrack(Graphics g, Rectangle bounds)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.TrackVertical.Normal, 1);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal thumb.
    /// </summary>
    public static void DrawHorizontalThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.Thumb.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a vertical thumb.
    /// </summary>
    public static void DrawVerticalThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbVertical.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a constant size left pointing thumb centered in the given bounds.
    /// </summary>
    public static void DrawLeftPointingThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbLeft.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a constant size right pointing thumb centered in the given bounds.
    /// </summary>
    public static void DrawRightPointingThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbRight.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a constant size top pointing thumb centered in the given bounds.
    /// </summary>
    public static void DrawTopPointingThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbTop.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a constant size bottom pointing thumb centered in the given bounds.
    /// </summary>
    public static void DrawBottomPointingThumb(Graphics g, Rectangle bounds, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbBottom.Normal, (int)state);

        t_visualStyleRenderer.DrawBackground(g, bounds);
    }

    /// <summary>
    ///  Renders a horizontal tick.
    /// </summary>
    public static void DrawHorizontalTicks(Graphics g, Rectangle bounds, int numTicks, EdgeStyle edgeStyle)
    {
        if (numTicks <= 0 || bounds.Height <= 0 || bounds.Width <= 0 || g is null)
        {
            return;
        }

        InitializeRenderer(VisualStyleElement.TrackBar.Ticks.Normal, 1);

        // trivial case -- avoid calcs
        if (numTicks == 1)
        {
            t_visualStyleRenderer.DrawEdge(g, new Rectangle(bounds.X, bounds.Y, LineWidth, bounds.Height), Edges.Left, edgeStyle, EdgeEffects.None);
            return;
        }

        float inc = ((float)bounds.Width - LineWidth) / ((float)numTicks - 1);

        while (numTicks > 0)
        {
            // draw the nth tick
            float x = bounds.X + (numTicks - 1) * inc;
            t_visualStyleRenderer.DrawEdge(g, new Rectangle((int)Math.Round(x), bounds.Y, LineWidth, bounds.Height), Edges.Left, edgeStyle, EdgeEffects.None);
            numTicks--;
        }
    }

    /// <summary>
    ///  Renders a vertical tick.
    /// </summary>
    public static void DrawVerticalTicks(Graphics g, Rectangle bounds, int numTicks, EdgeStyle edgeStyle)
    {
        if (numTicks <= 0 || bounds.Height <= 0 || bounds.Width <= 0 || g is null)
        {
            return;
        }

        InitializeRenderer(VisualStyleElement.TrackBar.TicksVertical.Normal, 1);

        // trivial case
        if (numTicks == 1)
        {
            t_visualStyleRenderer.DrawEdge(g, new Rectangle(bounds.X, bounds.Y, bounds.Width, LineWidth), Edges.Top, edgeStyle, EdgeEffects.None);
            return;
        }

        float inc = ((float)bounds.Height - LineWidth) / ((float)numTicks - 1);

        while (numTicks > 0)
        {
            // draw the nth tick
            float y = bounds.Y + (numTicks - 1) * inc;
            t_visualStyleRenderer.DrawEdge(g, new Rectangle(bounds.X, (int)Math.Round(y), bounds.Width, LineWidth), Edges.Top, edgeStyle, EdgeEffects.None);
            numTicks--;
        }
    }

    /// <summary>
    ///  Returns the size of a left pointing thumb.
    /// </summary>
    public static Size GetLeftPointingThumbSize(Graphics g, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbLeft.Normal, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    /// <summary>
    ///  Returns the size of a right pointing thumb.
    /// </summary>
    public static Size GetRightPointingThumbSize(Graphics g, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbRight.Normal, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    /// <summary>
    ///  Returns the size of a top pointing thumb.
    /// </summary>
    public static Size GetTopPointingThumbSize(Graphics g, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbTop.Normal, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    /// <summary>
    ///  Returns the size of a bottom pointing thumb.
    /// </summary>
    public static Size GetBottomPointingThumbSize(Graphics g, TrackBarThumbState state)
    {
        InitializeRenderer(VisualStyleElement.TrackBar.ThumbBottom.Normal, (int)state);

        return t_visualStyleRenderer.GetPartSize(g, ThemeSizeType.True);
    }

    [MemberNotNull(nameof(t_visualStyleRenderer))]
    private static void InitializeRenderer(VisualStyleElement element, int state)
    {
        if (t_visualStyleRenderer is null)
        {
            t_visualStyleRenderer = new VisualStyleRenderer(element.ClassName, element.Part, state);
        }
        else
        {
            t_visualStyleRenderer.SetParameters(element.ClassName, element.Part, state);
        }
    }
}
